The Connected World: Banking on Innovations in Photonic Sensors

The Internet of Things (IoT) is about to change how we live in almost every conceivable way, from driverless cars and smart cities to precision agriculture. In fact, the economic impact per year of all things IoT is projected to be $11.1 trillion a year by 2025, according to the global consulting firm McKinsey & Company.

Sensors capture data from the environment, automobiles, airplanes, trains, machines and machinery, buildings and people. Many of the 30 billion “things” that will ultimately be connected to the internet are expected to be relatively low-cost sensors for monitoring temperature, pressure, audio and acceleration, which will be wirelessly connected by WiFi, near-field communications (NFC), Bluetooth and other protocols. To meet the low-cost requirements, photonic sensor-related companies will be required to provide low-power solutions that include sensor transducers, microcontrollers, memory, power management and wireless connectivity. The question is: Which photonics technologies can achieve those demands?

EPIC Insights delves into advances and issues facing the photonics market throughout the European Union. It’s authored by the European Photonics Industry Consortium (EPIC). Courtesy of NTU.
With the exception of camera sensors, a photonic sensing system requires, by definition, a light source such as a laser or LED. The light source plays a similar role to that of a battery in electronic sensors, providing the light that interacts with the media, such as air or liquid, and measuring parameters such as pressure, temperature or the concentration of gases. The mandatory use of a light source in the system represents a problem when it comes to lowering power consumption, as well as cost. Photonic sensors become more efficient in cost, size and power consumption as the number of parameters measured increases. It stands to reason that the highly integrated multiparameter sensor is where the market opportunity for photonic sensors lies. Often these multiparameter sensors can be as small as a few micrometers and integrated in arrays in a silicon chip, as developed by Enschede, Netherlands-based LioniX.

Wearables leading the way

Consumer adoption of wearable technology is transforming how we track fitness. Multiparametric wearable technology has evolved from the iPod to smartwatches and fitness bands such as Fitbit, Jawbone UP and Nike’s FuelBand, designed for real-time personalized health monitoring and infotainment. But until recently, wearables have relied on microelectromechanical systems (MEMS)-based accelerometers that only infer caloric burn. Weight loss is more than a simple calculation of calories in and calories burned, as most of us have numerous, fluctuating variables in our personal weight-loss equation.

Users expect to see a marked distinction made between higher-cost and higher-functioning true medical-grade monitoring devices that track glucose, blood pressure and other biometric data, compared with the current generation of fitness products. That presents an opportunity for photonics-enabled, portable/wearable gas sensors. These sensors can monitor, for example, acetone as a measure of fat burn; alcohol and recreational drug abuse; and volatile organic compounds or chemicals in a vaporized state. Noninvasive breath monitoring of such compounds reveals clues about a person’s health, and has shown conclusive results in oncology, pulmonary disease, gastric disorders and renal failure, to name a few.

Exhaled breath contains trace biomarkers in the form of volatile organic compounds (VOCs), revealing changes in human physiology. Courtesy of Alpha Szenszor.
To support such activities, low-cost, low-power and yet high-resolution gas sensors are needed. Carbon nanotube sensors, like those developed by Worcester, Mass.-based Alpha Szenszor Inc., have shown the most promise in this field and offer the greatest advantage in terms of cost-performance metrics. For the new gas sensors to be included in these portable devices, however, very demanding specifications must be met. Sensitivity must reach parts per billion, and power consumption must come in at less than 50 microwatts. Plus, such sensors must be highly programmable and cost less than $1 per sensor.

Furthermore, the integration of functional nanomaterials with fabrics, coupled with microscale photonics, has shown significant progress for energy generation and self-health monitoring, as the signals can be transmitted via remote interface such as a mobile phone or smartwatch. The concept of humans wearing numerous sensors has also given rise to the concept of full virtual reality, which combines a vision system for the user, with commercially available virtual reality glasses, along with sensory capabilities. The commercial technology could become the next big thing by practically transforming the defense, security, gaming and landscape strategies from the design perspective.

Graphene and graphene-related materials are ideal for flexible electronic components, as graphene is inherently ultrathin, flexible, elastic and almost completely transparent. Graphene-based photonic sensors offer remarkable performance and can be used for pollution sensing, security, night vision and automotives, as well as health and fitness monitoring. The Spanish R&D institute ICFO has demonstrated wearable photonic sensors for fitness monitoring, such as heart rate and blood oxygen saturation. These ultrathin and wearable prototypes were exhibited recently at the mobile world congress in Barcelona. In the near future, more fitness and health markers will become available, with the potential to predict illness, fatigue, etc.

Consider the role of photonics technology in transforming our homes and vehicles. Real-time surveillance and remote- and intelligent-lighting systems are making our homes safer and enhancing our lifestyles; smart consoles and extensive sensor network-enabled smart vehicles have revolutionized our lives in an unprecedented way.

The “connected car” is a key part of the IoT. Safe driving is a main concern of the automotive industry, which is why the industry has integrated MEMS sensors for tracking tire pressure, engine performance and emergency stop-start systems. Over the next decade and beyond, fully or partially driverless car models will emerge, although it remains unclear how quickly such technology will be adopted as mainstream. Such cars will require a complex system of sensors for artificial vision. Gas sensors will be needed for monitoring air quality, with an emphasis on volatile organic compounds. Other sensors will monitor alcohol and drug abuse, with specific devices designed for gauging the presence of tetrahydrocannabinol (THC), responsible for most of cannabis intake-related psychological effects.

The tremendous potential of photonics coupled with IoT technology is bound to manifest itself in the development of smart cities and smart nations with the enabling state-of-the-art information and communication technologies, commonly known as ICT. The concept of smart cities is multifaceted in a way that it integrates the building blocks of any city’s traffic management, pollution control, intelligent lighting, energy and waste management systems. This extends to monitoring structures to ensure a comfortable and sustainable lifestyle for its occupants.

Inexpensive sensors cross-connected into a network offer much finer control over the physical elements of the urban landscape, from street lighting, public transportation, buildings and grounds. This control reduces costs by minimizing energy and resource waste, as well as increasing public safety by controlling lighting and remotely monitoring activities. Furthermore, one of the main priorities of these cities is to manage and monitor air quality. Gases have a huge impact on us and our environment, from oxygen as a life-sustaining gas to carbon dioxide (CO2) as the “villain in the sky” contributing to global warming. Sensing and eventually managing CO2 levels plays a significant, positive and varied role in our day-to-day lives with many social and economic benefits.

Current photonics companies are using mid-infrared-based sensors to track CO2, which absorbs at 4.26 µm. A good example is Glasgow, Scotland-based Gas Sensing Solutions (GSS), which has developed and ships unique solid-state CO2 sensors based on the NDIR (nondispersive infrared) optical method of sensing gas concentration. GSS sensors use specially developed solid-state LED and photodiode devices that feature low power consumption (<3.5 mW), rapid stabilization time (<2 s), and can be operated by applying short pulses for short duration measurements.

Optical fiber-based sensors can also play a major role in the sensing and connectivity of these smart cities. Fiber sensors using fiber Bragg gratings, Raman DTS (distributed temperature sensor) and Brillouin optical time domain reflectometry can be used in a radius of more than 100 km with the ability to measure temperature and strain at thousands of points in a single fiber.

Smart lighting, smart sensors for precision agriculture

Vertical farming is a component of urban agriculture, where the farming space is limited. It’s based on producing food in vertically stacked layers, vertically inclined surfaces and sometimes integrated into other structures. “Smart lighting” in horticulture combines lighting with environmental sensors, sensors that monitor crop growth and those that assess fertilizer and water levels. The control of environmental factors such as temperature, humidity and composition of gas, among others, will play an important role in improving the productivity of vertical farming. All of these environmental parameters can be monitored in real time using different photonic sensors including the above-mentioned fiber optics temperature/gas sensors and light sensors.

Integrated spectrometers developed by Apeldoorn, Netherlands-based Avantes or Ocean Optics Inc. in Dunedin, Fla., can provide affordable solutions for many of these applications. Acreo, a research and development center headquartered in Kista, Sweden, has created an optical system for following the development of the seedlings by measuring shoot height and total leaf area. In combination with software that adjusts to different plant colors, data processing will make it possible to follow plant growth in real time by a nondestructive method.

Mobile and home-based health care

Society is demanding more meaningful connected systems for disease management, preventive care and promoting healthy habits. Personalized home-based monitoring is exploding, given its many benefits: cost reduction, resource management and heightened awareness of the patient’s condition. This encompasses monitoring for prevention and maintenance of chronic conditions like diabetes.

Research for the development of portable, cost-effective preliminary screening devices has produced innovative imaging models for monitoring eye health, vision and early warning signs of chronic diseases like diabetes and hypertension. Photonics-enabled noninvasive technology can determine glucose concentrations in body fluid on contact. A successful demonstration is the handheld device by Glucosense Diagnostics, developed by a team of scientists at the University of Leeds, U.K. The device is based on variations of fluorescence light reflected by the skin with different glucose levels.

Another interesting example is point-of-care (POC) systems developed by Acreo for the detection of tuberculosis in sputum samples. The sputum sample is treated to become less viscous and compatible with an antibody-mediated labeling with fluorescent nanoparticles — quantum dots. The labeled bacteria are detected and counted by a low-cost flow cytometer. The technique has also been applied to the detection of E.coli bacteria in drinking water and raw water with the intention of integrating in the quality management of water utilities. The same basic technology can also be applied to marine biology for characterization of cyanobacteria and algae based on their endogenous fluorescent chlorophyll.

The IoT should bring a new era of convenience, functionality and utility to the way we live, travel, work and manage our health. The “smart” technologies will better anticipate our needs, reduce waste and improve the overall quality of our lives.

Meet the author

Jose Pozo is director of technology and innovation at EPIC (European Photonics Industry Consortium). He has 15 years’ background in photonics technology, market knowledge, and a large network within the industrial and academic photonics landscape. Jose is a member of the board of the IEEE Photonics Society, Benelux. He holds a Ph.D. in electrical engineering from the University of Bristol, U.K., and a M.Sc. and B.Eng. in telecom engineering from Spain/Belgium; email: jose.pozo@epic-assoc.com.